This invention relates to a protective material particularly but not solely for use in the manufacture of garments which would be used by motor cyclists to provide them with adequate protection against injury in accidents involving road surface impacts whilst not imposing an excessive thermal load on the rider in warm weather.
It is generally well known that motor cyclists, for example, will ride their motor cycles wearing normal street clothing which provides very little protection in road surface impacts, or will alternatively use specialist leather clothing which provides better protection. Racing motor cyclists almost always wear leather clothing but only high quality thick leather provides good protection in accidents. However, leather is in itself impermeable to wind and this leads to overheating of the rider during warm weather because body heat is retained causing excessive sweating inside the garment. To combat this effect perforated leather has been used but if a high visibility garment is worn over the perforated leather, such as the type of garment used by motor cycle traffic policemen, then air flow becomes considerably reduced with the resultant overheating of the motor cyclist in hot weather.
Impact protection has been provided in motorcycle riders' clothing for some years by the insertion of plastic or synthetic rubber foam materials, solid flexible materials, plastic sheet materials which may be somewhat stiffer and various combinations of these materials. Some or all of these layers are impermeable to wind. There are some designs of the material which do allow for air circulation within or below them relative to the skin of the rider. Disadvantageously, where this protection is held against the body by the clothing stretching over the knees, the movement is restricted and heat builds up generating sweat which leads to discomfort when the bike rider is too hot. In such garments as has been referred to, the evaporation of sweat from below the impact padding is not achieved using perforations in leather over or around the impact padding. This is also the case when normal street clothing fabrics, or normal woven motorcycle riders' fabric clothing are used because there is insufficient air movement beneath the impact protection in any of these combinations.
Therefore, for the protection of motor cyclists, for example, though the material qualities of leather have been found to be good, leather has to be perforated or provided with other systems to ventilate the clothing. Fabric clothing generally provides very poor protection from abrasions and cuts, and even high performance fabric clothing which is generally a multi-layer woven material and is impermeable to wind is still a poor protection from abrasions and cuts in a high speed accident. Any impact protection which is provided by foams, plastics etc. in pads is generally found to be impermeable to wind and sweat causing overheating of riders in hot weather. The sweat is not evaporated from below an impact protection material and consequently dampness builds up, adversely.
To overcome these particular problems manufacturers of such materials for use in protective clothing have utilised lightweight honeycomb materials of metal, plastics, paper and composites such as are used in construction boards and aerospace materials. These provide rigidity for particularly low weight. However, when honeycomb materials are used as impact energy absorbers the compression of the honeycomb structure of the rigid walls causes crumpling. The particular disadvantages to be found with such a material are that only one single use is possible because having crumpled their recovery is almost non-existent, and they are rigid.
Similar materials which are made from various plastics and welded into hexagonal cells or manufactured from parallel tubes bonded together will give flexible lightweight systems with some recovery after impacts. HEXCEL (Registered Trademark) and AEROLEN (Registered Trademark) are hexagonal cell materials which have been used in products such as trauma packs for wearing beneath ballistic armour. Although the products provide spacing between layers, some energy absorption, and are light, the performance of the products is not adequate for padding in motorcyclists clothing where the force level of impacts can be very high and thick materials are not acceptable in that they restrict movement.
Perforated plastics have been used in products such as football players' shin-guards but not with exclusively air permeable materials and sweat is therefore not able to evaporate through them. Although perforated foam materials have been used in footwear to "aid air circulation" they are generally used in conjunction with impermeable layers and therefore do not function to assist sweat evaporation.
The problem of allowing sweat to evaporate from adjacent to the skin has been met to some extent by some bulk air impermeable materials such as GORETEX (Registered Trademark) and AQUATEX (Registered Trademark) which are used in clothing. Because these products are fully windproof and do not permit bulk air movements sweat generated on the skin has to evaporate in relatively still air and to diffuse to the surface layer of the clothing, or the inner lining of the GORETEX or similar material, before escaping from the clothing. However, the amount of sweat which can be evaporated in this way with materials such as GORETEX is limited.